Part of the equation is how accurate of a rifle are you expecting, and what constitutes acceptable accuracy to you? Whether it is worth spending more for an upper usually depends on your expectations and end goals.

The differences in cost are a reflection of a number of things. Higher dollar uppers usually are made of "better" materials when it comes to things like metals. They may also more rigorously test their components with things like magnetic particle inspection (MPI), and HP testing.

Some of the higher dollar manufacturers also use processes during the build that can improve accuracy. The different rifling processes have their pros and cons. They also may do things like thermal fit the barrel to the upper. There also may be differences when it comes to QC checks.